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Publication numberUS5478620 A
Publication typeGrant
Application numberUS 08/203,481
Publication date26 Dec 1995
Filing date28 Feb 1994
Priority date18 Apr 1991
Fee statusLapsed
Publication number08203481, 203481, US 5478620 A, US 5478620A, US-A-5478620, US5478620 A, US5478620A
InventorsJoachim Mugge, Hubertus Ohm, Hans-Dieter Herrmann, Hans Ries
Original AssigneeHuels Aktiengesellschaft
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Multilayer plastic pipe
US 5478620 A
Abstract
Multilayer plastic pipes comprising a polyamide-based inner and outer layer, wherein the inner and outer layer are connected force-lockingly by means of at least one intermediate layer made of a mixture of a linear crystalline polyester and a polyamide, have improved stability to chemical agents and improved mechanical properties.
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Claims(9)
What is claimed as new and desired to be secured by Letters Patent of the United States is:
1. A multilayer plastic pipe, comprising polyamide inner and outer layers, wherein
said inner and outer layers are connected by means of at least one intermediate layer comprising (i) a mixture of a linear crystalline polyester and a polyamide or (ii) a polyester/polyamide copolymer, wherein said polyester and polyamide are present in a weight ratio ranging from 30 to 70:70 to 30.
2. The multilayer plastic pipe of claim 1, wherein said intermediate layer is a mixture of a crystalline polyester and a polyamide.
3. The multilayer plastic pipe of claim 1, wherein said intermediate layer is a polyester/polyamide copolymer.
4. The multilayer plastic pipe of claim 1, wherein said polyester and polyamide in said intermediate layer are present in a weight ratio ranging from 40 to 60:60 to 40.
5. The multilayer plastic pipe of claim 1, wherein said polyester in said intermediate layer is obtained by (poly)condensing an aliphatic diol, an alicyclic diol, or a mixture thereof with an aromatic dicarboxylic acid.
6. The multilayer plastic pipe of claim 1, wherein said intermediate layer comprises at least one polyamide selected from the group consisting of 4,6-; 6-; 6,6-; 6,12-; 8,10-; 10,10-; 10,12-; 11-; 12-; and 12,12-polyamide.
7. The multilayer plastic pipe of claim 1, which is a fuel pipe.
8. The multilayer plastic pipe of claim 1, which is an automobile fuel line.
9. A multilayer plastic pipe having polyamide inner and outer layers, wherein
said inner and outer layers are connected by means of an intermediate layer consisting of (i) a mixture of a linear crystalline polyester and a polyamide or (ii) a polyester/polyamide copolymer, wherein said polyester and polyamide are present in a weight ratio ranging from 30 to 70:70 to 30.
Description

This application is a continuation-in-part of application Ser. No. 07/833,701, filed on Feb. 11, 1992, now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to multilayer plastic pipe comprising a polyamide-based inner and outer layer.

Discussion of the Background

Plastic pipes made of polyamide are known and are used for a variety of applications. To fulfill their task, the pipes must be, among other things, inert to the medium flowing through them, and stable to high and low temperatures and mechanical stresses.

Single layer pipes are not always able to fulfill the necessary requirements. During transport of, e.g., aliphatic or aromatic solvents, fuels, or the like, they show significant drawbacks such as an insufficient barrier effect against the medium, undesired changes in dimensions or too little mechanical load bearing capacity.

An attempt was made to eliminate these drawbacks with multilayer pipes (DE-0SS 35 10 395 (corresponds to U.S. Pat. No. 5,038,833), 37 15 251 (corresponds to UK 2 204 376), 38 21 723, 38 27 092). The practical application of these proposals has shown, however, that individual drawbacks can be avoided, but the whole picture with respect to the physical properties is still unsatisfactory.

Thus, there remains a need for polyamide pipe with good barrier effect against the transported medium, satisfactory dimensional stability, and satisfactory mechanical load bearing capacity.

Summary of the Invention

Accordingly, it is one object of the present invention to provide novel polyamide pipe with a good barrier effect against the transported medium.

It is another object of the present invention to provide polyamide pipe with good dimensional stability.

It is another object of the present invention to provide polyamide pipe with good mechanical load bearing capacity.

These and other objects, which will become apparent during the following detailed description, have been achieved by the inventors' discovery that, by connecting together force-lockingly the inner and outer layer of the pipe by means of at least one intermediate layer made of a mixture of a linear crystalline polyester and a polyamide, pipes having good properties are obtained.

Detailed Description of the Preferred Embodiments

Suitable polyamides are primarily aliphatic homo- and copolycondensates. Examples are the 4,6-; 6,6-; 6,12-; 8,10-; 10,10-polyamides or the like. Preferred are 6-; 10,12-; 11-; 12- and 12,12-polyamides. The nomenclature of the polyamides corresponds to the international standard, where the first number(s) indicate(s) the carbon atom number of the starting diamine and the last number(s) indicate(s) the carbon atom number of the dicarboxylic acid. If only one number is given, this means that the polyamide is prepared from an α,ω-aminocarboxylic acid or from the lactam derived from it (see: H. Domininghaus, "The Plastics and their Properties" page 272, VDI Verlag (1976)).

If copolyamides are used, they can contain, e.g., adipic acid, sebacic acids, suberic acid, isophthalic acid, terephthalic acid as the coacid or bis(4'-aminocyclohexyl)methane, trimethylhexamethylenediamine, hexamethylenediamine as the codiamine.

The preparation of these polyamides is known (e.g., D. B. Jacobs, J. Zimmermann; Polymerization Processes, pages 425-67; Interscience Publishers, New York (1977); and DE-AS 2 152 194).

Mixed aliphatic/aromatic polycondensates, as described, e.g., in U.S. Pat. Nos. 2,071,250; 2,071,251; 2,130,523; 2,130,948; 2,241,322; 2,312,966; 2,512,606; 3,393,210 or in Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd. ed., vol. 18, pages 328 and 435, Wiley & Sons (1982), are also suitable as polyamides.

To the extent that it is necessary, the polyamides can also be made impact resistant. Suitable impact modifying components are products known, such as ethylene/propylene or ethylene/propylene/diene-copolymers (e.g., EP-OS 0 295 076); statistically or block-like synthesized copolymers comprising alkenyl aromatic compounds with aliphatic olefins or dienes (e.g., EP-OS 0 261 748); rubber types with a core/shell structure based on the (methy)acrylates, styrene, butadiene or the like (e.g., DE-OSS 37 28 685; 21 44 528), that can be functionalized optionally in accordance with the state of the art.

Polycondensates that are suitable as polyamides are also poly(ether ester amides) or poly(ether amides). Such products are described, e.g., in DE-OSS 27 12 987, 25 23 991, 30 06 961.

The molecular weight (number average) of the polyamides is suitably above 5,000, preferably above 10,000--in accordance with a relative viscosity (ηrel) ranging from 1.5 to 2.8.

The cited polyamides may be used alone or in mixtures.

Suitable linear crystalline polyesters have the following general structure formula (I) ##STR1## where R is a divalent branched or unbranched aliphatic and/or cycloaliphatic group having 2 to 12, preferably 2 to 8 carbon atoms in the carbon chain and R' is a divalent aromatic group having 6 to 20, preferably 8 to 12 carbon atoms in the carbon skeleton.

The linear crystalline polyesters may be prepared by condensing a diol with a diacid.

Examples of suitable diols are ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexanedimethanol, or the like.

Up to 25 mol % of the cited diol can be replaced by a second diol already cited above or by a diol with the following general formula (II)

HO--R"--O]x H                                         (II)

where R" is a divalent group having 2 to 4 carbon atoms and x can assume a value from 2 to 50.

Preferred diols are ethylene glycol and tetramethylene glycol.

A suitable aromatic dicarboxylic acid is, e.g., terephthalic acid, isophthalic acid, 1,4-; 1,5-; 2,6- or 2,7-naphthalene dicarboxylic acid, diphenic acid, diphenyl ether-4,4'-dicarboxylic acid.

Up to 20 mol % of these dicarboxylic acids can be replaced by aliphatic dicarboxylic acids such an succinic acid, maleic acid, fumaric acid, sebacic acid, dodecanedioic acid, etc.

The preparation of linear, crystalline polyesters is conventional in the art (DE-OSS 24 07 155, 24 07 156; Ullmann's Encyclopadie der technischen Chemie, 4th ed., vol. 19, page 65 ff.--Verlag Chemie GmbH, Weinheim, 1980).

The viscosity number, J, of the linear crystalline polyester of formula (I) is suitably 75 to 200 ml/g, preferably 100 to 175 ml/g, as measured in a 0.5 wt. % solution in an o-dichlorobenzene/phenol mixture (50:50 parts by weight) at 25° C. in accordance with DIN 53 728.

The compounds of polyamide and polyester that are used as the intermediate layer of the present invention may be prepared by mixing in any known manner. This mixture can also be further processed in the sense that the pellet mix is melted, e.g., in an extruder, mixed and repelletized. However, it is also possible to provide such a melt mixture additionally with catalysts and to convert in a known manner into copolycondensates (e.g. DE-AS 19 40 660; DE-OS 23 08 572; EP-OS 84 643).

Polyesters and polyamides are added to the intermediate layer in a weight ratio ranging from 30 to 70:70 to 30, preferably 40 to 60:60 to 40.

Conventional auxiliaries and additives such as stabilizers, processing aids, viscosity improvers, pigments, etc. can be added to the polyamide or polyester compounds.

Reinforcers or fillers such an glass fibers or glass beads, carbon fibers or mineral fibers can also be added to the polyamides intended for pipe application.

The multilayer plastic pipes can be manufactured in a known manner as described above, e.g., in the references cited in the discussion of the background. These references are incorporated herein by reference.

Although the exact dimensions of the present multilayer pipe may vary with the application for which the pipe is intended, good results have been achieved with pipes having: an outer polyamide layer with a thickness of 0.25 to 2.0 mm, preferably 0.50 to 1.5 mm, most preferably about 0.75 mm; an intermediate layer with a thickness of 0.05 to 0.25 mm, preferably 0.10 to 0.20 mm, most preferably about 0.15 mm; and an inner layer with a thickness of 0.05 to 0.15 mm, preferably 0.075 to 0.125 mm, most preferably about 0.10 mm. The external diameter may be 1 to 20 mm, preferably 5 to 15 mm, most preferably about 8 mm.

The multilayer plastic pipes of the invention exhibit an excellent stability and good barrier effect to diffusion with respect to transported media, in particular chemical agents, solvents, and fuels. Furthermore, the two polyamide layers are connected together so force-lockingly by means of the intermediate layer that the different layers do not shear, e.g., during thermal expansion or bending of the pipe. In addition to a three-layer pipe, pipes can also be manufactured that are made, e.g., of 5 or 7 layers by incorporating other layers made of polyamide or of polyamide/polyester.

Having generally described the invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.

EXAMPLES

The results given in the examples were determined with the aid of the following measuring methods.

The viscosity of the solution (viscosity number J) of the polyesters was determined by using a 0.5 wt. % solution in an o-dichlorobenzene/phenol mixture (50:50 parts by weight) at 25° C. in accordance with DIN 53 728.

The viscosity of the solution (rel. viscosity, ηrel) of the polyamides was determined by using a 0.5 wt. % cresol solution at 25° C. in accordance with DIN 53 727.

The diffusion of the fuel content was determined on sheetings by filling 50 ml of a fuel mixture (fuel M 15--42.5 parts by volume of isooctane, 42.5 parts by volume of toluene and 15 parts by volume of methanol) into a cylindrical container (diameter 5 cm, height 3 cm), which is sealed with the sheeting to be tested. The diffusion is determined at 23°±1° C. as loss in weight through diffusion over time (measurement every 24 hours). The maximum weight loss registered per area was given as the measure.

The frictional connection between the individual layers is determined with the aid of multilayer pipes or sheetings. In so doing, an attempt is made to separate the layers manually from one another, i.e., by bending the pipes or sheetings with subsequent separation test with a cutting tool and cross cutting. Pipes and sheetings are then categorized as "good" if the layers did not separate. Separation within a layer leads to the same categorization. Pipes and sheetings in which two layers separated are labelled "poor".

Tests that are labelled with letters are Comparative Examples, outside the scope of the present invention.

Examples

Added polycondensates

Polyamide components for the inner and outer layer:

PA 1: polyamide 12 (ηrel 1.9; amino end group content 80 mmol/kg)

PA 2: polyamide 12 (VESTAMID® L 2140; ηrel 2.1)

PA 3: polyamide 12 (VESTAMID® L 2124; ηrel 2.1 containing plasticizer)

Components for the intermediate layer:

Z1:

50 parts by weight of polyamide 12 (ηrel : 1.91; amino end group content: 80 mmol/kg; carboxyl end group content: 20 mmol/kg), 50 parts by weight of homo-poly(butylene terephthalate) (viscosity number J: 155 ml/g; carboxyl group content; 40 mmol/kg) and 0.1 parts by weight of triphenyl phosphite are continuously melt-mixed, extruded and granulated in a twin screw compounder rotating in the same direction (Leistritz model 30.34--jacket temperature: 260° C.; mass flow rate: 3 kg/h; screw velocity: 50 min-1).

Z2:

50 parts by weight of polyamide 12 (ηrel : 1.91; amino end group content: 80 mmol/kg; carboxyl end group content: 20 mmol/kg), 50 parts by weight of homo-poly(butylene terephthalate) (viscosity number J: 155 ml/g; carboxyl group content, 40 mmol/kg) and 0.1 parts by weight of dibutyl tin oxide are continuously melt-mixed, extruded and granulated in a twin screw compounder rotating in the same direction (Leistritz model 30.34--jacket temperature: 260° C.; mass flow rate: 3 kg/h; screw velocity: 50 min-1).

Z3:

100 parts by weight of homo-poly(butylene terephthalate) with predominantly hydroxyl end groups (J: 105 ml/g; OH: 80 mmol/kg, COOH: 20 mmol/kg) are converted with 11 parts by weight of a multi-functional commercially available isocyanate (IPDI T 1890-Huls-AG) in the melt at 250° C. and subsequently remelted, extruded, and granulated with a polyamide 12 (ηrel : 1.91; amino end group content: 80 mmol/kg; carboxyl end group content: 20 mmol/kg ).

Z4:

Ethylene vinyl alcohol copolymer, EVAL® EPF 101 A (Kurarai Company)

Z5:

Polyethylene, VESTOLEN® A 4042 (Huls AG)

Manufacture of sheetings and pipes

The sheetings are manufactured on a laboratory three layer sheeting system with a 400 mm three layer flat film die and a following three roller polishing stack. The extruder temperature during manufacture of the sheetings is set at 185° C. (PA 3); 200° C. (PA 1 and PA 2); 220° C. (Z5); 225° C. (Z4) and 245° C. (Z1 to Z3).

Pipes with 8 mm dimensions (outer diameter)×1 mm (overall wall thickness) and three layer construction are manufactured on a laboratory pipe extrusion system with a five layer pipe tool (outer layer: approximately 0.75 mm, intermediate layer; approximately 0.15 mm, inner layer: approximately 0.1 mm). All of the feed extruders exhibit a screw diameter of 25 mm. The cylinder temperature was at 220° C. (PA 3); 230° C. (PA 1, PA 2); 260° C. (Z1 to Z3); 240° C. (Z5); 200° C. (Z4).

              TABLE I______________________________________          inter- inner    mediate  outer                        frictional                                diffusiontest  layer    layer    layer                        connection                                (g · d-1 ·                                m-2)______________________________________1 F*) PA 1     Z 1      PA 1 good    1502 F   PA 2     Z 1      PA 2 good    1553 F   PA 3     Z 2      PA 1 good    1404 F   PA 2     Z 3      PA 3 good    1705 F   PA 3     Z 1      PA 3 good    1566 R*) PA 2     Z 1      PA 2 good    --7 R   PA 3     Z 3      PA 3 good    --A F   PA 2     Z 4      PA 2 poor    190B F   PA 3     Z 5      PA 1 poor    135C R   PA 2     Z 4      PA 2 poor    --D F   PA 3**)  --       --   --      1240E F   PA 2**)  --       --   --      635______________________________________ *) F = multilayer sheeting (layer thickness: approximately 0.1 mm) R = multilayer pipe **) single layer sheeting (layer thickness: approximately 0.1 mm)

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

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Non-Patent Citations
Reference
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5554426 *24 Mar 199510 Sep 1996Huels AktiengesellschaftMultilayer plastic pipe
US5637408 *5 Jun 199510 Jun 1997Huels AktiengesellschaftThermoplastic multilayer composite having a good adhesion between layers
US5798048 *28 May 199625 Aug 1998Huels AktiengesellschaftMultilayer plastic fuel filter having antistatic properties
US5858492 *29 Feb 199612 Jan 1999Huels AktiengesellschaftConsists of first layer of polyvinylidene fluoride, second layer comprises a mixture of polyamide and polyglutarimide, third layer is a coupling agent bonded to adjacent layers, and forth layer of polyolefin
US6090459 *7 Jul 199718 Jul 2000Huels AktiengesellschaftMultilayer plastic composition having an electrically conductive inner layer
US618019713 Feb 199830 Jan 2001Itt Manufacturing Enterprises, Inc.Multi-layer tubing having at least one intermediate layer formed from a polyamide/polyketone alloy
US62409701 Apr 19995 Jun 2001Itt Manufacturing Enterprises, Inc.Tubing for handling hydrocarbon materials and having an outer jacket layer adhered thereto
US625728113 Feb 199810 Jul 2001Itt Manufacturing Enterprises, Inc.Form motor vehicles
US62764008 Jun 199921 Aug 2001Itt Manufacturing Enterprises, Inc.Corrosion resistant powder coated metal tube and process for making the same
US642886612 Nov 19996 Aug 2002Degussa-Huels AktiengesellschaftMultilayer plastic composition having an electrically conductive inner layer
US65281253 Oct 20004 Mar 2003Itt Manufacturing Enterprises, Inc.Aerating zinc epoxy powder and polyvinylidene fluoride or nylon powder in fluidizing chambers; electrostatic charging; conveying, heating, curing; cooling, pulling while maintaining tension
US66700042 Aug 200030 Dec 2003Saint-Gobain Performance Plastics CorporationLaminated nylon air brake tubing
US71758969 Oct 200313 Feb 2007Degussa AgMolding material containing a polyamine-amide copolymer from a polyamine having at least 4 nitrogen atoms and a lactam, an aminocarboxyic acid and/or a combination of a dicarboxylic acid and a diamine; layer retained even after prolonged contact with alcohol or aqueous media or heat
US7914486 *23 Jan 200429 Mar 2011Boston Scientific Scimed, Inc.Catheter having an improved balloon-to-catheter bond
US804850422 Feb 20061 Nov 2011Evonik Degussa GmbhComposite having two or more layers, including an EVOH layer
US82218903 Oct 200517 Jul 2012Evonik Degussa GmbhMultilayer composite having a polyester layer and a protective layer
US844949728 Mar 201128 May 2013Boston Scientific Scimed, Inc.Catheter having an improved balloon-to-catheter bond
EP1378696A2 *24 Jun 20037 Jan 2004AtofinaHoses made of polyamide for compressed air
WO2007083041A2 *22 Jan 200726 Jul 2007Arkema FrancePolyamide hose for compressed air
Classifications
U.S. Classification428/36.91, 138/118.1, 138/127, 138/141, 428/36.9, 138/137, 138/125
International ClassificationF16L9/133
Cooperative ClassificationF16L9/133
European ClassificationF16L9/133
Legal Events
DateCodeEventDescription
7 Mar 2000FPExpired due to failure to pay maintenance fee
Effective date: 19991226
26 Dec 1999LAPSLapse for failure to pay maintenance fees
20 Jul 1999REMIMaintenance fee reminder mailed